Oil immersed fuse



Patented Oct. 27, 1931 UNITED STATES PATENT OFFICE FRIEDRICH NATALIS, OFBERLIN-CHARLOTTENBURG, GERMANY, ASSIGNOR TO WEST- INGHOUSE ELECTRIC ANDMANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA OIL IMMERSED ruseApplication filed November 5, 1925, Serial No. 67,013, and. in GermanyJanuary 23, 1925.

My invention relates to electric fuses or cutouts adapted to interruptan electric circuit upon the passage therethrough of abnormal anddangerous currents,'and it has particular relation to oil-immersed fusesfor high-tension currents.

It is an object of the present inventionto provide a fuse or cutoutwhereby the arc 1ncident to the rupture .of the fuse is quicklyextinguished and the circuit interrupted.

Another object of the invention is to provide an oil immersed fusewherein the oil surrounding the fuse is violently agitated and directedtoward the are upon the rupture of the fuse.

A fuse constructed in accordance with my invention comprises a cylinderof insulating material closed at the ends and having large openings atthe sides and fitted with a relatively light movable piston which isconnected to a terminal block at one end of the cylinder by a flexibleconductor and to a terminal block at the other end of the cylinder by afusible link. The piston is moved rapidly by the pressure of gasgenerated by the melting of the fuse, and the arc is extinguished by theinrush of quenching liquid.

In the accompanying drawings:

Figure 1 is a longitudinal sectional view of a fuse embodying featuresof the invention,

Fig. 2 is a reduced sectional view of an oil filled casing enclosing thefuse structure shown in Figure 1.

An insulating casing 11 is provided with two lateral openings 12 and 13and comprises an arc-extinguishing chamber 15 having a fusible wire 16located therein. The chamber is closed at the top by a cover 14, inwhich is located the detachable terminal member 17 to which is secured asecondary terminal member 18 for the fuse wire 16. The member 17 issecured to the cover 14 by the screw 19, which may also serve to securethe outside conductor to the device. The lower end of the fuse wire 16is connected, by means of a terminal member 20, to a link 21 and thislatter is connected to the terminal 23 by means of a flexible conductor22.

The link 21 is carried by a cup-like piston 24 that is provided withopenings 29 in its bottom and sides, respectively, the purpose of whichwill hereinafter appear. A tubular member 26, located within the member11, serves as a stop for the piston 24.

A metal re-inforcing casing 27 surrounds the casing 11 in order toprevent bursting thereof, and a packing ring 28 is provided at the jointbetween the cover 14 and the casing 11. The piston is made very light sothat it will move quickly when the fuse blows and prevent the side wallfrom being forced out, and. so that its movement will be dampened by theoil to prevent damage when it strikes the member 26.

The fuse structure above described is designed to be submerged in oil orother insulating liquid 30 contained in a tank 31, and, consequently,the fuse wire 16 and piston or plunger 24 are completely surrounded byinsulating fluid.

In the event of the passage of current greater than the rated capacityof the fusible element, the pressure generated by the arc resulting fromthe rupture of the fuse will move the piston rapidly and thus quicklyincrease the distance between the free ends of the fuse wire.

The large openings in the casing and in the piston allow the oil to Howin and quench the are formed by the melting of the fuse.

Oil also is permitted to flow inwardly through the openings 29 in theside of iston and across the are, thereby causing it to be rapidlycooled and extinguished. The rapid movement of the piston past theopenings 12 and 13 in the casing results in violent agitation of the oiland causes cool oil to flow into the space occupied by the are.

In order to replace the fuse wire 16, the casing is first removed fromthe tank and the terminal member 17 disengaged from the casing. A newfuse element may then be inserted between the member 17 and the link 21.The openings 29 in the sides of the piston 24 permit access to thefastening bolt or screw. I

The term electric fuse in the following claims means an electricconductor of such dimensions and other physical characteristics as to beheated to its melting point b current slightly in excess of the normalin Head current of apparatus connected in series with it, and used forthe purpose of protecting such apparatus. This use of the aforesaid termis its usual and well-known significance in the electric art.

It will be apparent from the foregoing description that the fuse deviceis simple and inexpensive in construction and that the parts thereof arereadily accessible for inspection, repair or replacement.

While I have described and illustrated a. particular form of theinvention, it will be apparent to those skilled in the art that variousmodifications, addition and omissions may be made therein withoutdeparting from the spirit and scope thereof. as set forth in theappended claims.

I claim as my invention:

1. In an electric fuse, the combination of a receptacle adapted tocontain insulating liquid, a tubular member made of insulating materialand disposed within said receptacle, said tubular member having largeopenings providing communication between the interior of the tubularmember and the liquid-containin portion of the receptacle, a

' closure for said tubular member spaced from the openings, said tubularmember forinin a chamber between the closure and sa'i openings, a pistondisposed within said tubular member, a fusible element disposed 'withinthe chamber and normally supporting the piston at the end of saidchamber adjacent said openings, said fusible element being fusible bythe passage of an excess electric current therethrough, whereby, uponmelting of said fusible element, the pressure of the gas generatedthereby will propel the piston away from said chamber to permit theinsulating liquid to enter through said openings into said chamber toextin uish the are.

2. In an electric fuse, the combination with an insulating casing closedat the ends and having substantially one half of its central portion cutaway, formin a large opening in its sides, of a fusible e ement and apiston therein located at one end of the opening, the said pistonbeingactuated t0 the other side of the opening by the pressure developedupon the rupturing of the fusible element.

3. In an electric fuse, the combination with an insulating casing havingits central portion cut away leaving large openings in its sides, of afusible element on one side of the openings, and a hollow .piston thatis movable past the opened central portion of the casing when propelledby the pressure of the ases developed upon the rupturing of the f usibleelement.

4. In an electric fuse, the combination with an insulating casing havingits upper. end closed to form a pressure chamber, the per- FRIEDRICHNATALIS.

